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The South African population of Roseate Tern Sterna dougalii breeds at a few small island colonies. Although the population has undergone large fluctuations, there are greater than 250 mature individuals in the region, satisfying the criteria for regionally Endangered under criterion D.
Roseate Terns have a large, fragmented global range, breeding in the western and eastern North Atlantic Ocean (North America, Azores, western Europe), from the Arabian Peninsula south to East Africa, Madagascar and South Africa, east to the Indian subcontinent, East Indies and into the western Pacific Ocean and south to Australia (Gochfeld 1983). Within the region, it breeds at Bird and St Croix islands in Algoa Bay and in small numbers at Dyer Island (Crawford et al. 2012). It has also been recorded breeding at Cape Recife (Randall and Randall 1980, Randall et al. 1991) where large pre- and post-breeding assemblages occur (Tree 2005). Birds are probably resident within the region with neither North Atlantic nor Indian Ocean birds known to migrate to southern Africa. Roseate Terns are present on their breeding islands from May to October but are present along the coast year-round (Tree 2005). The species breeds in two IBAs, both of which are protected, namely Algoa Bay Islands: Addo Elephant National Park (IBA SA095) and Dyer Island Nature Reserve (IBA SA120) (Underhill 2000).
The global population is estimated to be between 70 000 and 82 000 individuals (35 000 to 41 000 pairs; BirdLife International 2014). In 2010, 300 pairs were recorded in the region, but this number dropped to 100 pairs in 2011 (Crawford et al. 2012). The population is known to fluctuate but is thought be less than 250 mature individuals. Confidence in this regional population estimate is medium.
The global population trend is uncertain, as some populations are decreasing, while others are increasing or stable (Wetlands International 2006). Numbers of Roseate Terns breeding in South Africa have been low since population counts began in 1967. Breeding was recorded at Cape Recife in 1967 (39 pairs) and 1968 (71 pairs) but only roosting birds have been recorded since then. Low numbers of breeding pairs have been recorded at Dyer Island since 1971, ranging from no breeding to 20 pairs, with no clear upward or downward trend. At St Croix Island, 118-139 breeding pairs were recorded in 1977. Until 2003, counts have been erratic, and in some years only the presence of breeding birds has been recorded. In 2003, there were 30 breeding pairs at St Croix Island, which then increased to 58 in 2007 followed by a decrease to 25 in 2008 (Crawford et al. 2012). No Roseate Terns have been recorded breeding at this island from 2009. The species was first recorded breeding at Bird Island in 1977 and the first count (130 pairs) occurred in 1986. This colony reached a peak of between 240 and 250 breeding pairs from 1999 to 2001 and fluctuated in numbers from 2003 to 2010. The population is prone to a considerable amount of fluctuation although over a three generation period, the population trend is stable. Confidence in this regional trend estimate is medium.
Breeding Roseate Terns are vulnerable to disturbance as they do not return to their nests immediately when displaced (Underhill 2000), thus leaving eggs and chicks vulnerable to predation by Kelp Gulls Larus dominicanus. Chicks are vulnerable to hypothermia during cold, wet weather (Randall et al. 1991). In West Africa, decreases have been attributed to hunting (BirdLife International 2014).
No specific-specific conservation measures are currently underway in South Africa. Breeding sites on Bird and Dyer islands are protected as nature reserves. A control programme aimed at controlling number of the predatory Kelp Gull is ongoing at Bird Island, which is likely to benefit this species as well as other seabirds. Globally, efforts are underway to improve breeding habitat by constructing artificial nesting sites and nest boxes, vegetation management and flood control (BirdLife International 2014). The species is protected in terms of South Africa's Sea Birds and Seals Protection Act, No. 46 of 1973.
Disturbance at both breeding and roosting sites should be limited. A full study of what conservation measures will be most beneficial to Roseate Terns should also be conducted.
* The extent of post-breeding movements of Roseate Terns is imperfectly known, and should be researched.
* An investigation should be made into whether improving vegetation cover or providing artificial nests will improve breeding success as it has done elsewhere.
* The impact of predation by Kelp Gulls on eggs and chicks should be quantified.